Concentrated solution of a phosphate of a dyestuff of the Auramine series

Abstract

A concentrated phosphate solution of the base of a dyestuff of the Auramine series in a hydrophilic solvent (I), which solution is stable to storage and anhydrous; processes for the preparation of such a solution and use of such a solution for colouring paper or inks for flexography.

We claim: 
     
       1. A concentrated phosphate solution of the base of a dyestuff of the Auramine series in a hydrophilic solvent (I), which solution is stable to storage and anhydrous, said solvent being selected from the group consisting of propanol, furfuryl alcohol, tetrahydrofurfuryl alcohol, triethylene-glycol, glycol cyanohydrin, diacetone-alcohol, the methyl or ethyl ethers or thio-ethers of said solvents, acetic acid, propionic acid, glycolic acid, lactic acid, butylrolactone, methanol, ethanol, ethylene glycol, diethylene glycol, thiodiglycol, glycerine, glycol monochlorohydrin, formamide or a mixture of two or more said solvents. 
     
     
       2. Solution as claimed in claim 1 in which there is less than 0.1% by weight of water. 
     
     
       3. Solution as claimed in claim 1 in which the base of the dyestuff of the Auramine series is the base of Auramine G or the base of the Auramine obtained from N-ethyl ortho toluidine. 
     
     
       4. Solution as claimed in claim 1 in which the base of the dyestuff is the base of Auramine O or of ethylauramine. 
     
     
       5. Solution as claimed in claim 1 in which the phosphate concentration of the base of the dyestuff of the Auramine series is from 45% to 70% by weight. 
     
     
       6. Solution as claimed in claim 5 in which the phosphate concentration is higher than 50% by weight. 
     
     
       7. Solution as claimed in claim 5 in which the phosphate concentration is at least 55% by weight.